Spacer assembly



INVENTOR. MC. BURK M. c. BURK SPACER ASSEMBLY Filed June 20, 1955 mm IMI .July 15, 1958 i HMM United States Patent O M SPACER ASSEMBLY Marvin C. Burk, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application June 20, 1955, Serial No. 516,457

1 Claim. (Cl. 313-242) This invention relates to spacer assemblies. In one specific aspect, it relates to a vacuum tube wherein a shield and electrode are maintained at a predetermined spacing in a novel manner.

In the manufacture of various types of assemblies, it is necessary to provide accurate spacing of a pair of surfaces. This is particularly true of vacuum tubes, such as mass spectrometer tubes, wherein it is oftentimes necessary to support an electrodein an `accurately predetermined relationship to a shield or other element ofthe tube. It is desirable that such a spacing device have few or no parts protruding into the space adjacent the electrode which would interfere with collection of charged particlesby the electrode, and it is further highly desirable that no openings be required in the electrode so that the area thereof can `be most advantageously utilized.

In accordance With this invention, a plurality of 'spacer elements in the form of balls engageaflat surface of the electrode not exposed to the charged particles to be collected, and these balls t into openings in an adjacent shield or other part of the tube. A clamping device is arranged to force the electrode into engagement with the spacing balls and thus maintain the parts in an accurate predetermined arrangement without interfering with the collection of charged particles or cutting down the effective area of the electrode. Further in accordance with the invention, the shield to which the electrode is secured by the spacer balls is attached in a novel manner to an inwardly protruding portion of the tube envelope. This being effected by ears protruding from a slotted portion of the shield, which ears can be forced into clamping engagement, as by a set screw.

While the clamping device of the invention has particular application to vacuum tubes, such as mass spectrometer tubes, it will be evident from the following description that the device can be used to advantage in other types of assemblies where two parts must be maintained in accurate spaced relationship.

Accordingly, it is an object of the invention to provide an improved clamping assembly.

It is a further object to provide a novel electrode and shield assembly for a vacuum tube, such as a mass spectrometer tube.

It is a still further object to provide the aforementioned spacer assembly at a low cost, and with the use of a minimum number of parts of simple construction.

Various other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompaning drawings, in which:

Figure 1 is a view of a mass spectrometer tube embodying the electrode and spacing device of the invention;

Figure 2 is an end view of the electrode assembly;

Figure 3 is a sectional view taken along the line 3-3 of Figure 2, looking in the direction of the arrows; and

Figure 4 is a detail view illustrating a feature of the invention.

52,843,783 Patented July 15, 1958 tronic switch 19 to an oscillator, not shown. Each set titl 16 further includes outer electrodes 16h and 16C, and all of the electrodes 16h, 16e are connected through a resistance network 20 to a stepbac'k rectifier 21 and the aforementioned radio frequency oscillator. The stopping electrodes 17 are connected through a stopping detector 22 to the oscillator, and the suppressor grids 18, which collect secondary electrons, are connected to a negative terminal 23. The focusing electrodes 14, 15 are connected to potentiometers 25, 26 which, in turn, are connected between ground and a negative electrode 27 `to provide an adjustable variable negative potential upon these electrodes.

In operation, a sample material is introduced through an inlet 24, and ionized by electrons emitted from the fila- 'rnent `11. The resulting ions pass through the focusing elements 14 and 15. Ionsof a predetermined mass are selectively accelerated as `theyspass through the sets 16 of `control electrodes and the intervening field free drift spaces. Thus,ion's `of:a--precleterrnirred mass are preferentially collected attliewplate 12and cause a voltage representative thereof to appear at the output terminals 28. vAn `outlet 29 :is pro'vid'e'd which `is connected to a pump to` maintain ahigh'vacuum 'continuously in the tube.

The operation of the tube and associated circuitry is described in greater detail in the copending application of M. C. Burk and F. W. Karasek entitled Mass Spectrometer Emission Regulator led February 26, 1954.

In accordance with this invention, the assembly 12 is of novel construction, which is illustrated more particularly in Figures 2 and 3. Referring to these figures, it will be noted that the tube has an envelope 3S, preferably of glass, which supports a metal inwardly protruding portion 37 of generally cylindrical cross section. Secured to this protruding portion is a shield 38 which includes a relatively large cylindrical section 38a, a relatively small cylindrical section 38h, which fits over the cylindrical portion 37, and a transverse plate 38C joining these cylindrical sections.

The section 3811 has a longitudinal slot 39, Figure 4, formed in the end thereof and a pair of ears 40, 41 protrude radially outward from the respective edges 42 and 43 of this slot. These ears can be clamped together by one or more set screws 44, and it will be evident that this clamping action firmly secures the reduced section of the shield 38 to the cylindrical protruding portion 37 of the tube envelope.

The transverse plate 38e has a fiat surface 45, and it is provided with a plurality of openings 46 which are arranged in circular formation, as will be evident from Figure 2. These openings are preferably but not neces sarily of the same size. The assembly further includes a collector electrode 49 which has a smooth flat surface 50 opposing the surface 45 of the transverse plate 38C. A plurality of spacer balls 51 formed, for example, from glass or other insulating material, are mounted so that they engage the flat surface 50 of the electrode on the one hand and fit within the openings 46 in plate 38C on the other hand. These balls 51 are of larger size than the openings 46 and are preferably but not necessarily of the same size. When clamping pressure is exerted forcing the surface 50 into engagement with the balls 51, it will be evident that these balls function as spacing elements and maintain the parts in accurately spaced relationship.

The electrode 49 is further connected to a metal conductor rod 52 which extends axially through the cylindrical section 38b and through the cylindrical portion 37 of the tube envelope, a glass to metal seal 55 being provided between the conductor rod and the tube envelope. This seal is arranged to maintain the surface 50 of the electrode in clamping engagement with the spacer balls.

Accordingly, it will be evident that I have provided a novel mounting and spacing device which has general application, and has important specific application in vacuum tubes, particularly of the mass spectrometer type. In particular, in the latter application, it is not necessary to form holes for attachments or other features in the surface of the electrode and, consequently, the surface area of the electrode is all utilized advantageously for the collection of charged particles. Moreover, the Vpresence of insulating materials in close proximity to the electrode, which might accumulate a charge and interfere with proper operation, is substantially lessened by the novel shielding and spacing structure of the invention. Finally, there is an advantageous consolidation of parts in that the conductor rod, which carries the current from the electrode, constitutes the sole mechanical support for the electrode and no auxiliary supports are required. It will be evident that lche spacing structure itself is useful in many other applications where it is necessary to accurately space apart two smooth surfaces.

While the invention has been described in connection with a present, preferred embodiment thereof, it is to be understood that this description is illustrative only and is not intended to limit the invention.

I claim:

In a vacuum tube the combination of a glass envelope having a metal insert shaped to form an inwardly pro truding cylindrical portion, an internal metal shield having a relatively large cylindrical shielding section, a relatively small cylindrical support section and a transverse plate joining said sections, said relatively small cylindrical section slidably fitting over said inwardly protruding metal portion of said envelope, and said relatively small section having an axial slot formed at the end thereof, an ear protruding radially from each edge of the slot, a set screw clamping said ears together to secure said shield to said protruding portion, said transverse plate having a'plurality of openings formed therein, an electrode mounted within the relative large cylindrical portion of said shield, said electrode having a llat surface opposed to said transverse plate, a plurality of balls mounted in the respective openings and engaging the flat surface of said electrode, each ball being of larger diameter than its respective opening, a conductor rod secured to said electrode and extending axially through said relatively small cylindrical portion and through the tube envelope, a glass seal con- `necting said conductor to said metal portion at a position v where said at surface of the electrode is maintained in clamping engagement with said balls and a lament in said envelope, the entire surface of said electrode on the opposite side from said flat surface being imperforate and arranged to collect charged particles from said filament due to the arrangement of said balls and said transverse plate.

References Cited in the le of this patent UNITED STATES PATENTS 2,455,381 Morton et a1 Dec. 7, 1948 2,581,446 Robinson Jan. 8, 1952 2,644,101 Watrous June 30, 1953 2,726,335 Iske Dec. 6, 1955 2,782,337 Robinson Feb. 19, 1957 

